1. Technical Field
The present disclosure relates to a latent heat storage material.
2. Description of the Related Art
Use of heat storage materials is considered as one of the methods for effective utilization of thermal energy. Among heat storage materials, latent heat storage materials, which work by taking advantage of the phase change of materials, are advantageous in that they have a relatively high heat storage density and can maintain a constant temperature at which the phase change occurs. Among latent heat storage materials, sodium acetate trihydrate is considered to be suitable for various applications because it has a relatively large amount of latent heat of fusion and is non-toxic. For example, PTL 1 discloses a system in which sodium acetate trihydrate is used as a heat storage material. This conventional technique uses heat absorbed and released by phase change at or near melting point. On the other hand, there is also proposed a method for utilizing heat in a temperature zone lower than melting point. Specifically, in such a method, an aqueous sodium acetate solution as a heat storage material, resulting from dissolution of sodium acetate due to exhaust heat, stores heat when it is in what is called a supercooled state, where the solution maintains its liquid state even at a temperature lower than its melting point, and when necessary, a trigger is applied to the heat storage material, so that the heat storage material begins to crystallize and generate heat.
There are proposed heat storage material compositions capable of having improved stability of supercooled state for use in heat storage methods using a supercooled state as mentioned above. For example, PTL 2 discloses that when an aqueous caramel sugar solution or the like is added to sodium acetate trihydrate, the resulting heat storage material composition can stably maintain a supercooled state. PTL 3 discloses that when 10 wt % to 30 wt % of pure water is added to sodium acetate trihydrate, the resulting heat storage material composition can have a stabilized supercooled state in a low-temperature environment at −13° C. or lower.
Some applications or environments for systems using a heat storage material composition require the heat storage material composition to be capable of stably maintaining a supercooled state even in an environment at a temperature lower than room temperature (low-temperature environment).